System and methods for fabricating a component with laser array

ABSTRACT

An additive manufacturing system includes a laser array including a plurality of laser devices. Each laser device of the plurality of laser devices generates an energy beam for forming a melt pool in a powder bed. The additive manufacturing system further includes at least one optical element. The optical element receives at least one of the energy beams and induces a predetermined power diffusion in the at least one energy beam.

BACKGROUND

The subject matter disclosed herein relates generally to additivemanufacturing systems and, more particularly, to methods and systems forfabricating a component using a laser array by inducing power diffusionin energy beams generated by the laser array.

At least some additive manufacturing systems involve the buildup of ametal component to make a net, or near net shape component. This methodcan produce complex components from expensive materials at a reducedcost and with improved manufacturing efficiency. At least some knownadditive manufacturing systems, such as direct metal laser melting(DMLM) systems, fabricate components using an expensive, high-poweredlaser device and a powder material, such as a powdered metal. In someknown additive manufacturing systems, component quality may be reduceddue to excess heat and/or variation in heat being transferred to themetal powder by the laser device within the melt pool, creating a meltpool with varying depths.

In some known additive manufacturing systems, component quality isreduced due to the variation in conductive heat transfer between thepowdered metal and the surrounding solid material of the component. As aresult, the melt pool produced by the laser device may become too deep,resulting in the melt pool penetrating deeper into the powder bed,pulling in additional powder into the melt pool. The increased melt pooldepth may generally result in a poor surface finish of the component. Inaddition, in some known additive manufacturing systems, the component'sdimensional accuracy and small feature resolution may be reduced due tomelt pool variations because of the variability of thermal conductivityof the subsurface structures and metallic powder. As the melt pool sizevaries, the accuracy of printed structures can vary, especially at theedges of features. Controlling melt pool characteristics generallyrequires control of the heat transfer between the laser device and themelt pool including the power density of the beam spot generated by thelaser device used to melt the powdered material to form the melt pool.

BRIEF DESCRIPTION

In one aspect, an additive manufacturing system is provided. Theadditive manufacturing system includes a laser array including aplurality of laser devices. Each laser device of the plurality of laserdevices generates an energy beam for forming a melt pool in a powderbed. The additive manufacturing system further includes at least oneoptical element. The optical element receives at least one of the energybeams and induces a predetermined power diffusion in the at least oneenergy beam.

In another aspect, a method of fabricating a component in a powder bedis provided. The method includes emitting a plurality of energy beamsfrom a plurality of laser devices of a laser array. The method furtherincludes inducing, by an optical element, a power diffusion in at leastone energy beam of the plurality of energy beams and generating a meltpool, at least in part, with the at least one diffused energy beam.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic view of an additive manufacturing system;

FIG. 2 is a block diagram of a controller that is used to operate theadditive manufacturing system shown in FIG. 1;

FIG. 3 is a schematic view of an exemplary laser array for use with theadditive manufacturing system shown in FIG. 1;

FIG. 4 is a schematic view of an alternative laser array for use withthe additive manufacturing system shown in FIG. 1;

FIG. 5 is schematic view of yet another alternative laser array for usewith the additive manufacturing system shown in FIG. 1;

FIG. 6 is a schematic view of another alternative laser array for usewith the additive manufacturing system shown in FIG. 1;

FIG. 7 is a schematic diagram of a linear beam spot pattern andcorresponding power density distribution without an induced powerdiffusion;

FIG. 8 is a schematic diagram of a first beam spot pattern and acorresponding power density distribution that may be produced byinducing a first power diffusion to the beam spot pattern of FIG. 7;

FIG. 9 is a schematic diagram of a second beam spot pattern that may beproduced by inducing a second power diffusion to the beam spot patternof FIG. 7;

FIG. 10 is a schematic diagram of a third beam spot pattern that may beproduced by inducing a third power diffusion to the beam spot pattern ofFIG. 7;

FIG. 11 is a schematic diagram of a fourth beam spot pattern that may beproduced by inducing a fourth power diffusion to the beam spot patternof FIG. 7;

FIG. 12 is a schematic diagram of a beam spot array without an inducedpower diffusion;

FIG. 13 is a schematic diagram a first beam spot array that may beproduced by inducing a first power diffusion to the beam spot array ofFIG. 12;

FIG. 14 is a schematic diagram of a second beam spot array that may beproduced by inducing a second power diffusion to the beam spot array ofFIG. 12; and

FIG. 15 is a flow chart illustrating a method for fabricating acomponent in a powder bed.

Unless otherwise indicated, the drawings provided herein are meant toillustrate features of embodiments of the disclosure. These features arebelieved to be applicable in a wide variety of systems comprising one ormore embodiments of the disclosure. As such, the drawings are not meantto include all conventional features known by those of ordinary skill inthe art to be required for the practice of the embodiments disclosedherein.

DETAILED DESCRIPTION

In the following specification and the claims, reference will be made toa number of terms, which shall be defined to have the followingmeanings.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms such as “about,” “approximately,” and “substantially” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged; such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.

Furthermore, as used herein, the term “real-time” refers to at least oneof the time of occurrence of the associated events, the time ofmeasurement and collection of predetermined data, the time to processthe data, and the time of a system response to the events and theenvironment. In the embodiments described herein, these activities andevents occur substantially instantaneously.

As used herein, the terms “processor” and “computer” and related terms,e.g., “processing device,” “computing device,” and “controller” are notlimited to just those integrated circuits referred to in the art as acomputer, but broadly refers to a microcontroller, a microcomputer, aprogrammable logic controller (PLC), an application specific integratedcircuit, and other programmable circuits, and these terms are usedinterchangeably herein. In the embodiments described herein, memory mayinclude, but is not limited to, a computer-readable medium, such as arandom access memory (RAM), and a computer-readable non-volatile medium,such as flash memory. Alternatively, a floppy disk, a compact disc-readonly memory (CD-ROM), a magneto-optical disk (MOD), and/or a digitalversatile disc (DVD) may also be used. Also, in the embodimentsdescribed herein, additional input channels may be, but are not limitedto, computer peripherals associated with an operator interface such as amouse and a keyboard. Alternatively, other computer peripherals may alsobe used that may include, for example, but not be limited to, a scanner.Furthermore, in the exemplary embodiment, additional output channels mayinclude, but not be limited to, an operator interface monitor.

The systems and methods described herein facilitate manipulation ofenergy beams generated by lasers of a laser array to generate a desiredbeam spot pattern and corresponding power density across the beam spotpattern. Accordingly, system and methods described herein facilitateconsistent and predictable manufacturing of large areas during additivemanufacturing processes. Specifically, an additive manufacturing systemincludes an array of laser devices and at least one optical elementconfigured to induce a predetermined power diffusion in one or more ofthe energy beams generated by the laser devices. The laser arraygenerates a beam spot pattern, which may include, without limitation, alinear beam spot pattern or a two-dimensional beam spot array. Thepredetermined power diffusion generally results in a spreading orelongation of the effected beam spots such that the power density acrossat least a portion of the beam spot pattern containing the effected beamspots is modified. Such modification can be used to, without limitation,increase the uniformity or create a desired pattern of power densityacross a portion of the beam spot pattern. Such beam spot pattern mayinclude individual beam spot patterns and an aggregate spot shape whenconsidering multiple laser sources.

In the exemplary embodiment, for example, inducing the predeterminedpower diffusion includes inducing engineered optical aberrations, i.e.,beam distortions, to alter the laser intensity profile. Such engineeredoptical aberrations include, e.g., and without limitation, astigmatismin the energy beams such that an elongated beam spot having a moreuniform power density is produced. As described in more detail below,predetermined power diffusions may be selectively induced in one or moreof the energy beams to facilitate generation of various beam spotpatterns having different characteristics. In certain embodiments, theoptical elements are also coupled to an optical element actuator thatrepositions and/or reorients the optical elements to facilitatedynamically changing the induced power diffusion during operation of theadditive manufacturing system.

FIG. 1 is a schematic view of an exemplary additive manufacturing system10. A coordinate system 12 includes an x-axis, a y-axis, and a z-axis.In the exemplary embodiment, additive manufacturing system 10 includes alaser array 100 for fabricating a component 14 by a layer-by-layermanufacturing process. Laser array 100 includes a plurality of laserdevices, or emitters, 102, each of which provides a high-intensity heatsource configured to generate a melt pool 15 (not shown to scale) in apowdered material, i.e., powder bed 20 through an energy beam 104. Laserarray 100 is coupled to a mounting system 18. Additive manufacturingsystem 10 also includes a computer control system, or controller 16.Mounting system 18 is moved by an actuator or an actuator system 24 thatis configured to move mounting system 18 in an XY plane to facilitatefabricating a layer of component 14 with a sweep of laser array 100(i.e., requiring no scanning of laser array 100). For example, andwithout limitation, laser array 100 is pivoted about a central point tocover a circular portion of the powder on powder bed 20, moved in alinear path, a curved path, and/or rotated. Alternatively, laser array100 is moved in any orientation that enables additive manufacturingsystem 10 to function as described herein.

Actuator system 24 is controlled by controller 16 and moves laser array100 along a predetermined path about a powder bed 20, such as, forexample, and without limitation, linear and/or rotational paths.Alternatively, laser array 100 is stationary and energy beams 104 aremoved along the predetermined path by one or more galvanometers (notshown), for example, and without limitation, two-dimension (2D) scangalvanometers, three-dimension (3D) scan galvanometers, dynamic focusinggalvanometers, and/or any other scanning methods that may be used todeflect energy beams 104 of laser array 100.

In the exemplary embodiment, a powder bed 20 is mounted to a supportstructure 26, which is moved by actuator system 24. As described abovewith respect to mounting system 18, actuator system 24 is alsoconfigured to move support structure 26 in a Z direction (i.e., normalto a top surface of powder bed 20). In some embodiments, actuator system24 is also configured to move support structure 26 in the XY plane. Forexample, and without limitation, in an alternative embodiment wherelaser array 100 is stationary, actuator system 24 moves supportstructure 26 in the XY plane to direct energy beams 104 of laser array100 along a predetermined path about powder bed 20. In the exemplaryembodiment, actuator system 24 includes, for example, and withoutlimitation, a linear motor(s), a hydraulic and/or pneumatic piston(s), ascrew drive mechanism(s), and/or a conveyor system.

In the exemplary embodiment, optical fibers 108 are disposed betweenlaser array 100 and component 14. Optical fibers 108 are generallyconfigured to receive energy beams 104 from laser devices 102 of laserarray 100 and to direct energy beams 104 onto component 14. A height “H”defined between the array of optical fibers 108 (i.e., the free ends 112of optical fibers 108), or bundle 110 of optical fibers 108, and a toplayer 32 of component 14 is controlled by moving support structure 26 inthe Z direction. The height “H” is dependent on, for example, andwithout limitation, a type of energy beam 104 emitted by optical fibers108 (e.g., whether energy beams 104 are collimated, divergent, orconvergent), an output power of laser array 100, a pulse energy of laserarray 100, and/or a pulse width of laser array 100. More specifically.height H is determined to facilitate protecting laser devices 102 andassociated optics from soot and splatter that may rise from powder bed20. In the exemplary embodiment, free ends 112 of optical fibers 108 arelocated in a range between about 5 millimeters (mm) (0.197 inches (in))to about 150 mm (5.91 in) above powder bed 20 so that any region of alayer of powder bed 20 can be melted by actuating laser array 100.

In the exemplary embodiment, at least one optical element 150 isdisposed between optical fibers 108 and component 14. Optical element150 includes, without limitation, one or more of a refractive lens, suchas a cylindrical lens, and a reflective mirror. In general, lightexiting the fibers is natively divergent and some form of optics isneeded to focus laser beams 104 onto powder bed 20. As such, in additionto adding the beam distortions, i.e., aberrations (discussed furtherbelow), optical element 150 is further configured to provide laser beamfocusing as well as some minor lens shaping to add the intended spotdistortion. While, for illustrative purposes, the figures generally showlight from laser devices 102 as single pencil lines or diverging linesafter optic element 150, as is known in optic physics, laser beams 104will tend to actually spread out upon transmission from laser devices102 and optical element 150 is used to refocus them onto powder bed 20.Therefore, the primary role of optical element 150 is to focus exitinglight into a small spot at the working plane. Optical element 150 maynot necessarily be spherical, but rather have unequal curvatures toprovide different degrees of focus in the X-Y plane to facilitateforming non-circular spots and hence facilitating smearing of one spotinto another. Therefore, in addition to laser beam focusing, opticalelement 150 is generally configured to induce a power diffusion in oneor more energy beams 104.

For purposes of this disclosure, the term “power diffusion” generallyrefers to a reduction in the power density of a beam spot produced byone of energy beams 104 on a surface of component 14 or powder bed 20.The reduction in power density is achieved by a spreading or smearingwhich results in, without limitation, one or more of an elongation ofthe beam spot and an increase in the area of the beam spot. In theexemplary embodiment, optical element 150 has unequal curvature in theX-Y plane, and while not purely cylindrical, it has a generallycylindrical lens configured to induce a power diffusion in at least oneof energy beams 104. More particularly, optical element 150 may not bejust a single optic, but may include multiple lenses operating inaggregate. For example, and without limitation, in one embodiment,optical element uses a substantially spherical lens, i.e., substantiallyequal curvature and focal lengths in the X-Y plane along with a secondcylindrical lens stacked before or after the first lens which inducesthe smearing in a single dimension. The curvature of lens, refractiveindex (if it is not a mirrored surface) and distance between elementsall contribute to the effective focal length of the complete system inthe X-Y plane. As such, regardless of the specific configuration,optical element 150 induces engineered optical aberrations that include,e.g., and without limitation, astigmatism in energy beam 104 in laserbeams 104 such that an elongated beam spot having a more uniform powerdensity is produced. Astigmatism generally refers to a condition inwhich each of two orthogonal axial cross-sections of energy beam 104have a different focal length. Accordingly, when a beam havingastigmatism is projected at a focal length in which one of the twoprincipal cross-sections is in focus, the other of the two principlecross-sections is not in focus. The resulting effect is the productionof an elongated beam spot at each of the focal lengths.

In the exemplary embodiment, additive manufacturing system 10 isoperated to fabricate component 14 from an electronic representation ofthe 3D geometry of component 14. The electronic representation may beproduced in a computer aided design (CAD) or similar file. The CAD fileof component 14 is converted into a layer-by-layer format that includesa plurality of build parameters for each layer of component 14, forexample, top layer 32 of component 14. In the exemplary embodiment,component 14 is arranged electronically in a desired orientationrelative to the origin of the coordinate system used in additivemanufacturing system 10. The geometry of component 14 is sliced into astack of layers of a desired thickness, such that the geometry of eachlayer is an outline of the cross-section through component 14 at thatparticular layer location. A “toolpath” or “toolpaths” are generatedacross the geometry of a respective layer. The build parameters areapplied along the toolpath or toolpaths to fabricate that layer ofcomponent 14 from the material used to construct component 14. The stepsare repeated for each respective layer of component 14 geometry. Oncethe process is completed, an electronic computer build file (or files)is generated, including all of the layers. The build file is loaded intocontroller 16 of additive manufacturing system 10 to control the systemduring fabrication of each layer.

After the build file is loaded into controller 16, additivemanufacturing system 10 is operated to generate component 14 byimplementing the layer-by-layer manufacturing process, such as a directmetal laser melting method. The exemplary layer-by-layer additivemanufacturing process does not use a pre-existing article as theprecursor to the final component, rather the process produces component14 from a raw material in a configurable form, such as a powder. Forexample, and without limitation, a steel component can be additivelymanufactured using a steel powder. Additive manufacturing system 10enables fabrication of components, such as component 14, using a broadrange of materials, for example, and without limitation, metals,ceramics, glass, and polymers.

FIG. 2 is a block diagram of controller 16 that is used to operateadditive manufacturing system 10 (shown in FIG. 1). In the exemplaryembodiment, controller 16 is one of any type of controller typicallyprovided by a manufacturer of additive manufacturing system 10 tocontrol operation of additive manufacturing system 10. Controller 16executes operations to control the operation of additive manufacturingsystem 10 based at least partially on instructions from human operators.Controller 16 includes, for example, a 3D model of component 14 to befabricated by additive manufacturing system 10. Operations executed bycontroller 16 include controlling power output of laser array 100 (shownin FIG. 1) and adjusting mounting system 18 and/or support structure 26,via actuator system 24 (all shown in FIG. 1), to control the scanningspeed of laser array 100 within additive manufacturing system 10.

In the exemplary embodiment, controller 16 includes a memory device 60and a processor 62 coupled to memory device 60. Processor 62 may includeone or more processing units, such as, without limitation, a multi-coreconfiguration. Processor 62 is any type of processor that permitscontroller 16 to operate as described herein. In some embodiments,executable instructions are stored in memory device 60. Controller 16 isconfigurable to perform one or more operations described herein byprogramming processor 62. For example, processor 62 may be programmed byencoding an operation as one or more executable instructions andproviding the executable instructions in memory device 60. In theexemplary embodiment, memory device 60 is one or more devices thatenable storage and retrieval of information such as executableinstructions or other data. Memory device 60 may include one or morecomputer readable media, such as, without limitation, random accessmemory (RAM), dynamic RAM, static RAM, a solid-state disk, a hard disk,read-only memory (ROM), erasable programmable ROM, electrically erasableprogrammable ROM, or non-volatile RAM memory. The above memory types areexemplary only, and are thus not limiting as to the types of memoryusable for storage of a computer program.

Memory device 60 may be configured to store any type of data, including,without limitation, build parameters associated with component 14. Insome embodiments, processor 62 removes or “purges” data from memorydevice 60 based on the age of the data. For example, processor 62 mayoverwrite previously recorded and stored data associated with asubsequent time or event. In addition, or alternatively, processor 62may remove data that exceeds a predetermined time interval. In addition,memory device 60 includes, without limitation, sufficient data,algorithms, and commands to facilitate monitoring of build parametersand the geometric conditions of component 14 being fabricated byadditive manufacturing system 10.

In some embodiments, controller 16 includes a presentation interface 64coupled to processor 62. Presentation interface 64 presents information,such as the operating conditions of additive manufacturing system 10, toa user 66. In one embodiment, presentation interface 64 includes adisplay adapter (not shown) coupled to a display device (not shown),such as a cathode ray tube (CRT), a liquid crystal display (LCD), anorganic LED (OLED) display, or an “electronic ink” display. In someembodiments, presentation interface 64 includes one or more displaydevices. In addition, or alternatively, presentation interface 64includes an audio output device (not shown), for example, withoutlimitation, an audio adapter or a speaker (not shown).

In some embodiments, controller 16 includes a user input interface 68.In the exemplary embodiment, user input interface 68 is coupled toprocessor 62 and receives input from user 66. User input interface 68may include, for example, without limitation, a keyboard, a pointingdevice, a mouse, a stylus, a touch sensitive panel, such as, withoutlimitation, a touch pad or a touch screen, and/or an audio inputinterface, such as, without limitation, a microphone. A singlecomponent, such as a touch screen, may function as both a display deviceof presentation interface 64 and user input interface 68.

In the exemplary embodiment, a communication interface 70 is coupled toprocessor 62 and is configured to be coupled in communication with oneor more other devices, such as laser array 100, and to perform input andoutput operations with respect to such devices while performing as aninput channel. For example, communication interface 70 may include,without limitation, a wired network adapter, a wireless network adapter,a mobile telecommunications adapter, a serial communication adapter, ora parallel communication adapter. Communication interface 70 may receivea data signal from or transmit a data signal to one or more remotedevices. For example, in some embodiments, communication interface 70 ofcontroller 16 may transmit/receive a data signal to/from actuator system24.

Presentation interface 64 and communication interface 70 are bothcapable of providing information suitable for use with the methodsdescribed herein, such as, providing information to user 66 or processor62. Accordingly, presentation interface 64 and communication interface70 may be referred to as output devices. Similarly, user input interface68 and communication interface 70 are capable of receiving informationsuitable for use with the methods described herein and may be referredto as input devices.

FIG. 3 is a schematic view of laser array 100 of additive manufacturingsystem 10 (shown in FIG. 1). In the exemplary embodiment, laser array100 includes plurality of laser devices 102, each of which provides ahigh-intensity heat source configured to generate melt pool 15 (shown inFIG. 1) in a powdered material, i.e., powder bed 20 (shown in FIG. 1).Each laser device 102 is configured to emit an energy beam 104. Laserarray 100 also includes a plurality of lenses 106 positioned betweenlaser devices 102 and a plurality of optical fibers 108. Lenses 106 areconfigured to couple energy beam 104 emitted by a respective laserdevice 102 to a respective optical fiber 108. In the exemplaryembodiment, optical fibers 108 are provided in a bundle 110 betweenlaser devices 102 and free ends 112 of optical fibers 108. Inalternative embodiments, laser array 100 includes laser devices that donot use coupling optics, such as lenses 106, as discussed herein.Disposed between free ends 112 and component 14 is an optical element150 configured to induce a power diffusion of energy beams 104 as energybeams 104 travel between free ends 112 and component 14. In theexemplary embodiment, optical element 150 is a cylindrical lensconfigured to induce engineered optical aberrations in energy beams 104as energy beams 104 travel between optical fibers 108 and component 14.Alternatively, optical element 150 has any configuration that enablesoperation of additive manufacturing system 10 as described herein,including, without limitation, the configurations described above.

FIG. 4 is a schematic view of an alternative laser array 400 for usewith additive manufacturing system 10 (shown in FIG. 1). Laser array 400includes a plurality of laser devices 402, each of which provides ahigh-intensity heat source configured to generate melt pool 15 (shown inFIG. 1) in a powdered material, i.e., powder bed 20 (shown in FIG. 1).Each laser device 402 is configured to emit an energy beam 404 of laserenergy. Laser array 400 also includes a plurality of lenses 406positioned between laser devices 402 and a plurality of optical fibers408. Lenses 406 are configured to couple energy beam 404 emitted by arespective laser device 402 to a respective optical fiber 408. In laserarray 400, optical fibers 408 are provided in a bundle 410 between laserdevices 402 and free ends 412 of optical fibers 408. Free ends 412 areoptically coupled to optical elements 450, which are configured toinduce a power diffusion in energy beams 404 as energy beams 404 exitfree ends 412. As described above for optical element 150 (shown inFIGS. 1 and 3), optical elements 450 are also configured to focus laserbeams 404.

FIG. 5 is a schematic view of yet another alternative laser array 500for use with additive manufacturing system 10 (shown in FIG. 1). Laserarray 500 includes a plurality of laser devices 502, each of whichprovides a high-intensity heat source configured to generate melt pool15 (shown in FIG. 1) in a powdered material, i.e., powder bed 20 (shownin FIG. 1). Each laser device 502 is configured to emit an energy beam504 of laser energy. Laser array 500 also includes a plurality of lenses506 positioned adjacent laser devices 502 and configured to directenergy beams 404 emitted by respective laser devices 502. In contrast tolaser array 100 and laser array 400 (shown in FIGS. 3 and 4respectively), laser array 500 does not include optical fibers betweenlaser devices 502 and component 14. Laser array 500 includes an opticalelement 550 configured to induce a power diffusion in only a subset ofenergy beam 504 as the subset of energy beams 504 travels between laserdevices 502 and component 14.

FIG. 6 is a schematic view of still another alternative laser array 600for use with additive manufacturing system 10 (shown in FIG. 1). Laserarray 600 includes a plurality of laser devices 602, each of whichprovides a high-intensity heat source configured to generate melt pool15 (shown in FIG. 1) in a powdered material, i.e., powder bed 20 (shownin FIG. 1). Each laser device 602 is configured to emit an energy beam604 of laser energy. Laser array 600 also includes a plurality of lenses606 positioned adjacent laser devices 602 and configured to directenergy beams 604 emitted by respective laser devices 602. Laser array600 includes a plurality of optical elements 650, each optical element650 corresponding to a respective laser device 602, configured to inducea power diffusion in energy beams 604 as energy beams 604 travel betweenlaser devices 602 and component 14.

In laser array 600, optical elements 650 are arranged in an opticalelement array 652 coupled to an optical element actuator 654. Opticalelement actuator 654 is configured to manipulate one or more of opticalelements 650 during operation of additive manufacturing system 10. Forexample, in certain embodiments, optical element actuator 654 isconfigured to manipulate optical element array 652 as a whole. In otherembodiments, optical element actuator 654 is coupled to and configuredto manipulate only a subset of optical elements 650. In still otherembodiments, laser array 600 includes a plurality of optical elementactuators 654, each optical element actuator configured to individuallymanipulate one or more optical elements 650 of the optical element array652.

Optical element actuator 654 is generally configured to manipulate oneor more of optical elements 650 by changing one or more of anorientation and displacement of the one or more optical elements 650.The displacement and orientation may be relative to laser devices 602,component 14, or any other suitable component of additive manufacturingsystem 10. By changing orientation and/or position of optical elements650, optical element actuator 654 facilitates dynamic modification ofthe power diffusion of energy beams 604. For example, in one embodiment,an optical element 650 may produce a first power diffusion when in afirst orientation and a second power diffusion in a second orientationand optical element actuator 654 may selectively change optical element650 from the first orientation to the second orientation. In otherembodiments, optical element actuator 654 is configured to remove anoptical element 650 from the path of an energy beam 604 such that theenergy beam 604 is not subject to power diffusion. In still otherembodiments, optical element actuator 654 is configured to selectivelyexchange a first optical element with one or more second opticalelements to facilitate changing power diffusion.

To facilitate control of optical element actuator 654, optical elementactuator 654 may be communicatively coupled to an optical elementactuator controller 656. In certain embodiments, optical elementactuator controller 656 is communicatively coupled to controller 16(shown in FIGS. 1 and 2) and configured to receive instructions fromcontroller 16. In alternative embodiments, optical element actuatorcontroller 656 is integrated into controller 16.

FIG. 7 is a schematic diagram of a linear beam spot pattern 700 and acorresponding power density distribution 702 without induced powerdiffusion. Power density distribution 702 is shown as incoherentirradiance (power per unit area) as a function of spatial position withrespect to the x-axis (shown in FIG. 1). Referencing FIGS. 1, 3, and 7,beam spot pattern 700 is provided as a reference pattern of beam spots704. More specifically, beam spot pattern 700 corresponds to anunaltered beam spot pattern, such as would be produced by energy beams104 generated by laser devices 102 during operation of additivemanufacturing system 10 absent power diffusion by optical element 150.As indicated in power density distribution 702, each beam spot 704generally includes a peak power intensity 706 at the center of each beamspot 704 that declines to low power at the extent of each beam spot 704.Accordingly, as laser array 100 sweeps in a first direction 750 during amanufacturing process, laser array 100 may not adequately melt powderedmaterial disposed within low power intensity gaps 708. Similarly, aslaser array 100 sweeps in a second direction 752, low power intensitygaps 708 may result in unwanted cooling of melt pool 15 (shown in FIG.1).

FIG. 8 is a schematic diagram of first beam spot pattern 800 and acorresponding power density distribution 802 that may be produced byinducing a first power diffusion to beam spot pattern 700 (shown in FIG.7). Power density distribution 802 is shown as incoherent irradiance(power per unit area) as a function of spatial position with respect tothe x-axis (shown in FIG. 1). In contrast to the substantially circularbeam spots 704 of beam spot pattern 700 (shown in FIG. 7), beam spots804 are subject to power diffusion facilitated by an optical element,such as optical element 150 (shown in FIGS. 1 and 3). For example, incertain embodiments, optical element 150 induces an engineered opticalaberration in each of beams 104 such that elongated beam spots 804 areproduced on the surface of component 14. As indicated in power densitydistribution 802, the resulting arrangement of elongated beam spots 804produces a more uniform power distribution across a beam pattern length856 of beam spot pattern 800 as compared to beam spot pattern 700.Accordingly, as laser array 100 is translated in a first direction 850,relatively uniform power density is provided across beam spot pattern800, thereby approximating a single, wide beam. Similarly, as laserarray 100 is translated in a second direction 852, relatively uniformpower is provided along the length of beam spot pattern 800 as comparedto beam spot pattern 700, thereby providing more uniform power exposureas beam spot pattern 800 is translated in second direction 852.

FIGS. 9-12 are schematic diagrams of alternative beam spot patterns thatmay be produced using additive manufacturing machines in accordance withthis disclosure, such as additive manufacturing system 10 (shown in FIG.1).

FIG. 9 shows a second beam spot pattern 900 that may be produced byinducing a second power diffusion to the beam spot pattern of FIG. 7. Toproduce second beam spot pattern 900, one or more optical elements, suchas optical element 150 (shown in FIG. 1), induce a power diffusion suchthat beam spots 904 are elongated in a direction substantiallyperpendicular to a beam pattern length 956.

FIG. 10 shows a third beam spot pattern 1000 that may be produced byinducing a third power diffusion to the beam spot pattern of FIG. 7. Toproduce third beam spot pattern 1000, one or more optical elements, suchas optical element 150 (shown in FIG. 1), induce a power diffusion thatvaries across a beam pattern length 1056. More specifically, the one ormore optical elements induce a power diffusion that causes the beamspots of beam spot pattern 1000 to progressively vary from beingelongated in a direction substantially parallel to beam pattern length1056 to a direction substantially perpendicular to beam pattern length1056. Beam spot pattern 1000 further exhibits diffusion of beam spots1004 such that beam spots 1004 increase in area along a portion of beampattern length 1056. In alternative embodiments, beam spots 1004 of beamspot pattern 1000 vary in other ways along beam pattern length 1056including varying, without limitation, one or more of elongation, area,decreasing in area, and orientation.

FIG. 11 shows a fourth beam spot pattern 1100 that may be produced byinducing a fourth power diffusion to the beam spot pattern 700 of FIG.7. To produce fourth beam spot pattern 1100, one or more opticalelements, such as optical element 150 (shown in FIG. 1), induce a powerdiffusion to one or more subsets of beams 104 (shown in FIG. 1). Forexample, in beam spot pattern 1100, the one or more optical elementsinduce a power diffusion that elongates a beam spot subset 1106 of beamspots 1104 in a direction substantially parallel with a beam patternlength 1156. In contrast, extent beam spots 1108 are not subject topower diffusion and have higher power density than beam spot subset1106. Due to the increased power density of extent beam spots 1108, beamspot pattern 1100 facilitates formation of components having moreclearly defined edges. In alternative embodiments, beam spot subset 1106may be oriented in any suitable direction including, without limitation,substantially perpendicular to beam pattern length 1156 and diagonalwith respect to beam pattern length 1156.

FIG. 12 is a schematic diagram of a beam spot array 1200 without inducedpower diffusion. Beam spot array 1200 is intended to illustrate areference pattern of beam spots 1204. More specifically, beam spot array1200 corresponds to an unaltered beam spot array such as would beproduced by an additive manufacturing system having a two-dimensionallaser array and absent power diffusion by an optical element. Beam spotarray 1200 generally includes a two-dimensional arrangement of beamspots 1204 arranged in a plurality of beam spot rows 1206 defining abeam spot array length 1208 and a beam spot array width 1210.

FIGS. 13 and 14 are schematic diagrams of alternative beam spot arraysthat may be produced using additive manufacturing machines in accordancewith this disclosure, such as additive manufacturing system 10 (shown inFIG. 1).

FIG. 13 is a schematic diagram of a first beam spot array 1300 that maybe produced by inducing a first power diffusion to the beam spot array1200 of FIG. 12. To produce first beam spot array 1300, one or moreoptical elements, such as optical element 150 (shown in FIG. 1), inducea power diffusion to one or more of beams 104 (shown in FIG. 1). Forexample, beam spot array 1300 generally includes a two-dimensionalarrangement of beam spots 1304 arranged in a plurality of beam spot rows1306 defining a beam spot array length 1308 and a beam spot array width1310. In the exemplary embodiment, the one or more optical elements 150induce a power diffusion that elongates each beam spot 1304 in adirection that is substantially perpendicular to beam spot array length1308, i.e., in the direction of beam spot array width 1310.Alternatively, the one or more optical elements 150 induce a powerdiffusion that elongates each beam spot 1304 in a direction that issubstantially perpendicular to beam spot array width 1310, i.e., in thedirection of beam spot array length 1308. In other alternativeembodiments, the one or more optical elements 150 induce other powerdiffusions, such as those described in FIGS. 9-12 with respect to alinear beam spot pattern. For example, the one or more optical elementsmay induce a power diffusion that results in, without limitation, one ormore of a predetermined elongation, diffusion, and orientation of one ormore of beam spots 1304.

FIG. 14 is a schematic diagram of a second beam spot array 1400 that maybe produced by inducing a second power diffusion to the beam spot array1200 of FIG. 12. To produce second beam spot array 1400, one or moreoptical elements, such as optical element 150 (shown in FIG. 1), inducea power diffusion to energy beams 104 (shown in FIG. 1). In beam spotarray 1400, beam spots 1404 are arranged in a plurality of beam spotrows 1406. For example, beam spot array 1400 generally includes atwo-dimensional arrangement of beam spots 1404 arranged in a pluralityof beam spot rows 1406 defining a beam spot array length 1408 and a beamspot array width 1410. The one or more optical elements 150 induce apower diffusion that elongates and reorients each beam spot 1404. Morespecifically, beam spots 1404 in each beam spot row 1406 are elongatedand reoriented in a direction substantially diagonal relative to beamspot rows 1406, i.e., diagonal to beam spot array length 1408 and beamspot array width 1410. Further, beam spots 1404 are reoriented to extendperpendicularly with respect to beam spots 1404 in adjacent beam spotrows 1406. For example, each beam spot 1404 in a first beam spot row1404 is elongated in a first diagonal direction and a second beam spotrow is elongated in a second diagonal direction substantiallyperpendicular to the first diagonal direction. The resulting beam spotarray 1400 provides a substantially uniform power density across thefull area of beam spot array 1400, particularly as compared to theunaltered beam spot array 1200 shown in FIG. 12. In other alternativeembodiments, beam spots 1404

FIG. 15 is a flow chart illustrating a method 1500 for fabricating acomponent 14 in a powder bed. Referring to FIGS. 3 and 15, method 1500includes emitting 1502 a plurality of energy beams 104 from a pluralityof laser devices 102 of a laser array 100. Laser array 100 and, morespecifically, laser devices 102 are arranged to produce a beam spotpattern. In certain embodiments, laser devices 102 are arranged in asubstantially linear configuration to produce a corresponding linearbeam spot pattern. In alternative embodiments, laser devices arearranged in a two-dimensional array to produce a correspondingtwo-dimensional beam spot array.

Method 1500 further includes inducing 1502, by an optical element 150, apower diffusion in at least one of energy beams 104. Optical element 150is generally disposed between laser devices 102 and component 14 suchthat as energy beam 104 travels from laser device 102 to component 14,optical element 150 induces a power diffusion in energy beam 104. Thepower diffusion induced by optical element 150 generally results in oneor more of elongation, diffusion, and reorientation of a beam spotcorresponding to beam 104. For example, in the exemplary embodiment,power diffusion is induced by inducing astigmatism in energy beam 104such that the resulting beam spot is elongated. In certain embodimentsoptical element 150 includes, without limitation, at least one of arefractive lens (such as a cylindrical lens) and a reflective mirror.

Method 1500 further includes generating 1504 a melt pool with the atleast one diffused energy beam. As described in more detail above in thecontext of FIG. 1, the diffused energy beam 104 is directed to a powderbed 20 and used to selectively melt powder of powder bed 20 into meltpool 15. At the melt pool cools and solidifies, a portion of a layer ofcomponent 14 is formed.

The embodiments described herein improve control of energy beamsproduced by laser devices of an array of lasers for use in an additivemanufacturing process. More specifically, the embodiments describeherein facilitate inducement of a predetermined power diffusion in theenergy beams and, as a result, generation of a beam spot pattern havinga predetermined power density distribution. Such control facilitatestailoring the power density distribution to improve the overall additivemanufacturing process. For example, the systems and methods describedherein can be used to form preferential melt pool characteristics, suchas a consistent melting depth. The system and methods further facilitateadditive manufacturing of large areas as compared to single lasersystems, reducing manufacturing time and costs for a given component

An exemplary technical effect of the methods, systems, and apparatusdescribed herein includes at least one of: (a) controlling power densityof a beam spot pattern generated by a laser array; (b) generating a beamspot pattern having a predetermined power density by inducing apredetermined power diffusion in one or more beams of the laser array;and (c) dynamically changing a power density of a beam spot pattern bymanipulating one or more optical elements.

Exemplary embodiments of additive manufacturing systems including alaser array and optical element configured to induce a predeterminedpower diffusion are described above in detail. The systems and methodsdescribed herein are not limited to the specific embodiments described,but rather, components of systems and/or steps of the methods may beutilized independently and separately from other components and/or stepsdescribed herein. For example, the methods may also be used incombination with other laser fabrication systems and methods, and arenot limited to practice with only the systems and methods, as isdescribed herein. Rather, the exemplary embodiments can be implementedand utilized in connection with many additive manufacturing systemapplications.

Although specific features of various embodiments of the disclosure maybe shown in some drawings and not in others, this is for convenienceonly. In accordance with the principles of the disclosure, any featureof a drawing may be referenced and/or claimed in combination with anyfeature of any other drawing.

Some embodiments involve the use of one or more electronic or computingdevices. Such devices typically include a processor, processing device,or controller, such as a general purpose central processing unit (CPU),a graphics processing unit (GPU), a microcontroller, a reducedinstruction set computer (RISC) processor, an application specificintegrated circuit (ASIC), a programmable logic circuit (PLC), a fieldprogrammable gate array (FPGA), a digital signal processing (DSP)device, and/or any other circuit or processing device capable ofexecuting the functions described herein. The methods described hereinmay be encoded as executable instructions embodied in a computerreadable medium, including, without limitation, a storage device and/ora memory device. Such instructions, when executed by a processingdevice, cause the processing device to perform at least a portion of themethods described herein. The above examples are exemplary only, andthus are not intended to limit in any way the definition and/or meaningof the term processor and processing device.

This written description uses examples to disclose the embodiments,including the best mode, and also to enable any person skilled in theart to practice the embodiments, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal language of the claims.

What is claimed is:
 1. An additive manufacturing system comprising: alaser array comprising a plurality of laser devices, each laser deviceof said plurality of laser devices configured to generate an energy beamfor forming a melt pool in a powder bed; and an optical elementconfigured to receive at least one of the energy beams and to induce apredetermined power diffusion in the at least one energy beam.
 2. Theadditive manufacturing system of claim 1, wherein said at least oneoptical element is configured to induce the predetermined powerdiffusion by inducing beam distortion in the at least one energy beam.3. The additive manufacturing system of claim 1, wherein said at leastone optical element is one of a refractive lens and a reflective mirror.4. The additive manufacturing system of claim 1, wherein said pluralityof laser devices are further configured to produce a substantiallylinear beam spot pattern having a beam spot pattern length, each beamspot of the beam spot pattern corresponding to one of the energy beams.5. The additive manufacturing system of claim 4, wherein thepredetermined power diffusion elongates at least one of the beam spotsin a direction that is at least one of substantially parallel andsubstantially perpendicular to the beam spot pattern length.
 6. Theadditive manufacturing system of claim 4, wherein the predeterminedpower diffusion varies along the beam pattern length.
 7. The additivemanufacturing system of claim 6, wherein the predetermined powerdiffusion varies by at least one of increasing along a portion of thebeam pattern length, decreasing along a portion of the beam patternlength, and having a first power diffusion at extents of the beam spotpattern and a second power diffusion within the beam spot pattern. 8.The additive manufacturing system of claim 1, wherein said plurality oflaser devices are further configured to produce a two-dimensional beamspot array having a beam spot array length and a beam spot array width,each beam spot of the beam spot array corresponding to one of the energybeams.
 9. The additive manufacturing system of claim 8, wherein thepredetermined power diffusion elongates at least one of the beam spotsin a direction that is one of substantially parallel to the beam spotarray length and substantially parallel to the beam spot array width.10. The additive manufacturing system of claim 8, wherein thepredetermined power diffusion diagonally elongates at least one of thebeam spots relative to each of the beam spot array length and the beamspot array width.
 11. The additive manufacturing system of claim 8,wherein: the beam spot array includes a plurality of beam spot rows; andthe predetermined power diffusion diagonally elongates each beam spot ina first beam spot row of the plurality of beam spot rows in a firstdiagonal direction relative to each of the beam spot array length andthe beam spot array width.
 12. The additive manufacturing system ofclaim 11, wherein the predetermined power diffusion diagonally elongateseach beam spot in a second beam spot row of the plurality of beam spotrows in a second diagonal direction substantially perpendicular to thefirst diagonal direction.
 13. The additive manufacturing system of claim1 further comprising at least one actuator coupled to said at least oneoptical element, said at least one actuator configured to at least oneof reorient and reposition said at least one optical element.
 14. Theadditive manufacturing system of claim 1 further comprising a pluralityof optical fibers, each optical fiber configured to receive an energybeam from a corresponding laser device of said plurality of laserdevices.
 15. The additive manufacturing system of claim 1, wherein theat least one optical element is integrated into a free end of at leastone optical fiber of the plurality of optical fibers.
 16. A method offabricating a component in a powder bed comprising: emitting a pluralityof energy beams from a plurality of laser devices of a laser array;inducing, by an optical element, a power diffusion in at least oneenergy beam of the plurality of energy beams; and generating a meltpool, at least in part, with the at least one diffused energy beam. 17.The method of claim 16 wherein inducing the power diffusion in at leastone energy beam of the plurality of energy beams further comprisesinducing beam distortion in the at least one energy beam.
 18. The methodof claim 16 wherein: emitting the plurality of energy beams produces asubstantially linear beam spot pattern have a beam spot pattern length,each beam spot of the beam spot pattern corresponding to one of theenergy beams; and inducing the power diffusion elongates at least one ofthe beam spots in a direction that is at least one of substantiallyparallel to the beam spot array length and substantially parallel to thebeam spot array width
 19. The method of claim 16 wherein: emitting theplurality of energy beams produces a two-dimensional beam spot arrayhaving a beam spot array length and a beam spot array width, each beamspot of the beam spot array corresponding to one of the energy beams;and inducing the power diffusion elongates at least one of the beamspots in a direction that is at least one of substantially parallel tothe beam spot array length and substantially parallel to the beam spotarray width.
 20. The method of claim 16, wherein: emitting the pluralityof energy beams produces a two-dimensional beam spot array having a beamspot array length, a beam spot array width, and a plurality of beam spotrows, each beam spot of the beam spot array corresponding to one of theenergy beams; and inducing the predetermined diffusion furthercomprises: diagonally elongating each beam spot in a first beam spot rowof the plurality of beam spot rows in a first diagonal directionrelative to each of the beam spot array length and the beam spot arraywidth; and diagonally elongating each beam spot in a second beam spotrow of the plurality of beam spot rows in a second diagonal directionsubstantially perpendicular to the first diagonal direction.